Thread forming machine

Abstract

The present invention relates to a thread forming machine (1) for producing an internal thread in a metal workpiece, the thread forming machine (1) comprising a forming section (6) having a common central rotation axis (7), wherein the forming section (6) comprises a plurality of lubrication grooves (8) extending parallel to the rotation axis (7), the forming section (6) comprises a plurality of ridge segments (9) extending along the circumference of the forming section (6), the plurality of ridge segments (9) being arranged for forming the internal thread in the metal workpiece, and wherein, in the circumferential direction, every two ridge segments of the plurality of ridge segments (9) are separated by one lubrication groove of the plurality of lubrication grooves (8). At least one of the lubrication grooves (8) is asymmetric about any radius (10) intersecting a surface (11) of the one lubrication groove (8) when projected into a projection plane perpendicular to the rotation axis (7).

Description

Technical Field

[0001] The present disclosure relates to a thread forming machine for manufacturing an internal thread in a metal workpiece, the thread forming machine comprising: a shaft having a first end and a second end; a mounting section connected to the first end of the shaft for mounting the thread forming machine to a spindle of a machine tool; and a forming section connected to the second end of the shaft, wherein the shaft, the mounting section and the forming section have a common central rotation axis extending in a longitudinal direction, wherein the forming section comprises a plurality of lubrication grooves extending parallel to the rotation axis, and wherein the forming section comprises a plurality of ridge segments extending along a circumference of the forming section, wherein the plurality of ridge segments are arranged for forming an internal thread in the metal workpiece, and wherein in a circumferential direction, every two ridge segments of the plurality of ridge segments are separated by one of the plurality of lubrication grooves. Background Art

[0002] There are many different types of thread formers, sometimes also referred to as thread forming tools. Thread formers create internal threads in metal workpieces without any material removal action, such as cutting or chip removal. One type of thread former has a forming section provided with a plurality of ridge segments arranged at the periphery of the forming section to form an internal thread. In other words, the plurality of ridge segments in the forming section of the thread former are arranged in the shape of a circumferential spiral. Some thread formers include a plurality of lubrication grooves extending parallel to the axis of rotation. In the circumferential direction, every two ridge segments of the plurality of ridge segments are separated by one of the plurality of lubrication grooves. The process of forming an internal thread in a metal workpiece using such a thread former comprises inserting the thread former into an existing hole while rotating the thread former about its central axis of rotation and moving the tool axially forward. Typically, the maximum radial extension of the forming section measured relative to the axis of rotation is greater than the radius of the existing hole. The ridge segments are pressed into the surface of the workpiece, causing the cylindrical hole wall of the existing hole to be reshaped or deformed, thereby forming the internal thread.

[0003] Due to this reshaping of the workpiece, thread formers operating without cutting the workpiece are subject to severe stress, high wear and high temperatures. Sometimes, thread formers suffer from crack formation at the ridge section of the forming section. Summary of the invention

[0004] An object of the present disclosure is to provide a thread former with an extended tool life. Another object is to provide a thread former with improved wear resistance.

[0005] At least one of the above objects is achieved by the invention as defined in the appended claims.

[0006] According to one aspect of the present disclosure, at least one of the above-mentioned purposes is solved by a thread former for manufacturing an internal thread in a metal workpiece. The thread former includes: a shaft having a first end and a second end; a mounting section connected to the first end of the shaft for mounting the thread former to a spindle of a machine tool; and a forming section connected to the second end of the shaft. The shaft, the mounting section and the forming section have a common central axis of rotation, which extends in a longitudinal direction. The forming section includes a plurality of lubrication grooves extending parallel to the axis of rotation. The forming section includes a plurality of ridge segments extending along the periphery of the forming section, wherein the plurality of ridge segments are arranged to form an internal thread in a metal workpiece. In addition, in a circumferential direction, every two ridge segments of the plurality of ridge segments are separated by one of the plurality of lubrication grooves. At least one of the lubrication grooves is asymmetric about any radius intersecting a surface of the one lubrication groove when projected into a projection plane perpendicular to the axis of rotation.

[0007] The basic idea of ​​the thread former according to the present disclosure is to provide at least one lubrication groove of the plurality of lubrication grooves with asymmetry. This asymmetry is visible when two ridge segments of the plurality of ridge segments separated by the one lubrication groove of the plurality of lubrication grooves are projected into a plane perpendicular to the axis of rotation (i.e., the projection plane). The outer contour of the projection corresponds well to the outer contour of the thread former visible to an observer in an axial view with the forming segment of the thread former as the top.

[0008] According to the present disclosure, the flanks of the ridge segments adjacent to the lubrication grooves are designed differently, which results in an asymmetric lubrication groove. As a result, the ridge segments have a stronger and / or more stable flank at one of their sides. Thus, due to the asymmetry of at least one of the lubrication grooves, a stronger and / or more stable tool with an extended tool life can be achieved.

[0009] According to an embodiment of the present disclosure, one of the two ridge segments adjacent to the one lubrication groove may be designed to provide enhanced strength, while the other of the two ridge segments adjacent to the one lubrication groove may be designed to provide additional space for cooling and lubrication fluid, thereby avoiding premature reduction of the free cross-sectional area of ​​the one lubrication groove. Thus, the ridge segments are strengthened and efficiently cooled / lubricated at the same time.

[0010] Thus, a thread former having a ridge segment with increased strength at one of its flanks and a lubrication groove efficiently supplying cooling and / or lubricating fluid is achieved. Thus, a thread former having extended tool life and wear resistance is provided.

[0011] The plurality of ridge segments are arranged for forming an internal thread in a metal workpiece. In other words, the plurality of ridge segments are arranged along a spiral path around a common rotation axis, wherein the cross-section of each of the plurality of ridge segments substantially corresponds to the cross-sectional form of the groove in the internal thread to be produced.

[0012] There are thread formers with helical lubrication grooves extending at a helix angle relative to the axis of rotation. However, the present disclosure relates to a thread former with a plurality of lubrication grooves extending parallel to the axis of rotation and not inclined relative to the axis of rotation.

[0013] The rotation direction of the thread former according to the present disclosure is designed so that an internal thread with a desired hand direction can be manufactured in a metal workpiece. Therefore, each of the plurality of ridge segments has a leading end point at its periphery, which is the leading point of the ridge segment when the thread former rotates in the rotation direction. In addition, each of the plurality of ridge segments has a trailing end point at its periphery, which is the trailing end point of the ridge segment when the thread former rotates in the rotation direction.

[0014] In an embodiment of the present disclosure, when the forming segment of the thread former is projected into the projection plane, the forming segment of the thread former has a polygonal shape. Specifically, as seen in the projection, the forming segment has an overall polygonal shape along the periphery of the ridge. The corners of the polygon are formed by the points of maximum radial extension of the plurality of ridge segments.

[0015] In an embodiment, wherein the endpoints of two ridge segments adjacent to the one lubrication groove among the plurality of ridge segments have different radial distances from the rotation axis, according to the present disclosure, a lubrication groove is considered to be asymmetric if the lubrication groove is asymmetric until the radial distance from the rotation axis is equal to the smaller radial distance of the two endpoints of the adjacent forming ridges.

[0016] In an embodiment of the present disclosure, the asymmetry of the lubrication groove is also visible in a cross section perpendicular to the axis of rotation and extending through two of the plurality of ridge segments and the one of the plurality of lubrication grooves. Due to the spiral arrangement of the plurality of ridge segments, the endpoints of the leading and trailing webs of the lubrication groove are at different radial distances from the axis of rotation. In this case and in the sense of the present disclosure, the shape of the one lubrication groove is evaluated only until the radial distance from the axis of rotation is equal to the smaller of the radial distances of those endpoints.

[0017] In an embodiment of the present disclosure, when each of the plurality of lubrication grooves is projected into a projection plane perpendicular to the axis of rotation, each of the plurality of lubrication grooves is asymmetric about any radius intersecting the surface of the corresponding lubrication groove. Therefore, each of the plurality of lubrication grooves provides the advantages of the at least one asymmetric lubrication groove. In addition, in an embodiment of the present disclosure, when each of the plurality of lubrication grooves is projected into a projection plane, each of the plurality of lubrication grooves has the same shape. Therefore, each of the plurality of lubrication grooves can be manufactured using the same one or more tools.

[0018] In an embodiment of the present disclosure, at least one of the lubrication grooves extends only in the forming section of the thread former. In an embodiment of the present disclosure, each of the plurality of lubrication grooves extends only in the forming section of the thread former. In another embodiment of the present disclosure, at least one of the lubrication grooves extends in the forming section of the thread former and in the shaft of the thread former. In an embodiment, each of the plurality of lubrication grooves extends in the forming section of the thread former and in the shaft of the thread former. The extension of at least one of the lubrication grooves in the shaft enables effective delivery of lubricating fluid into the hole during internal thread forming, even after the forming section has been screwed into the hole over its entire axial extension.

[0019] In an embodiment of the present disclosure, any radius is a segmentation radius that segments the one lubrication groove among the plurality of lubrication grooves into a first portion and a second portion, wherein the segmentation radius intersects the surface of the one lubrication groove among the plurality of lubrication grooves at the lowest point having the smallest radial distance from the rotation axis. This feature balances sufficient support of one side of the ridge segment adjacent to the one lubrication groove and effective delivery of lubrication fluid in the one lubrication groove.

[0020] In an embodiment of the present disclosure, at least the one lubricating groove is asymmetrical along the entire longitudinal extension of the lubricating groove in the profiled section and optionally also in the shaft. Due to the asymmetry along the entire axial extension, a support function is provided for all ridge segments along the axial extension. Furthermore, in an embodiment, the one lubricating groove is manufactured along its entire axial extension in the profiled section and optionally also in the shaft using a single grinding tool.

[0021] In an embodiment of the thread former according to the present disclosure, the surface of the one lubricating groove extends from the trailing end point of the first of the two ridge segments to the leading end point of the second of the two ridge segments. The surface of the one lubricating groove has a lowest point, which has the smallest radial distance from the rotation axis. In addition, the one lubricating groove includes two partial surfaces, wherein the first partial surface extends from the trailing end point of the first ridge segment to the lowest point, and the second partial surface extends from the lowest point to the leading end point of the second ridge segment.

[0022] In view of this, there are two different designs of the claimed asymmetry of the one lubrication groove. In a first embodiment, the asymmetry of the one lubrication groove provides support for the trailing end of the first spine segment, and in a second embodiment, the asymmetry of the one lubrication groove provides support for the leading end of the second spine segment.

[0023] In an embodiment, any radius is a segmentation radius that segments the one lubrication groove into a first portion and a second portion, wherein the segmentation radius intersects the surface of the one lubrication groove at the lowest point having the minimum radial distance from the axis of rotation. When the first portion and the second portion are projected onto the projection plane, the first portion is limited by the surface of the first portion, and the second portion is limited by the surface of the second portion. In a first embodiment, the cross-sectional area of ​​the first portion of the one lubrication groove is smaller than the cross-sectional area of ​​the second portion. In this first embodiment, the asymmetry of the lubrication groove supports the strength and stability of the tail end of the first spine segment. In a second embodiment, the cross-sectional area of ​​the first portion of the one lubrication groove is larger than the cross-sectional area of ​​the second portion. In this second embodiment, the asymmetry of the lubrication groove supports the strength and stability of the front end of the second spine segment. In both embodiments, the larger area of ​​the second portion of the lubrication groove can be designed to compensate for the smaller area of ​​the first portion, thereby ensuring sufficient flow of the lubrication fluid.

[0024] In an embodiment of the present disclosure, when the first portion and the second portion of the lubrication groove are projected into a projection plane, the area of ​​the first portion and the area of ​​the second portion of the lubrication groove are respectively measured as the areas between the first portion surface and the second portion surface, the dividing plane, and the straight line connecting the tail end of the first ridge segment and the front end of the second ridge segment.

[0025] In an embodiment of the thread former according to the present disclosure, when projected into the projection plane, the second part surface has a concave curvature along its entire extension from the lowest point to the front end point of the second spine segment, and the first part surface is shorter than the second part surface. In this embodiment, significantly more material is left at the trailing end of the first spine segment, which provides improved stability for the trailing end of the first spine segment. At the same time, the concave shape of the second part surface provides sufficient flow of lubricating fluid through the one lubrication groove.

[0026] In an embodiment of the thread former according to the present disclosure, at least a portion of the first part surface is straight when projected into the projection plane. A straight part surface is easy to machine (eg by grinding) and provides considerable stability by avoiding peak loads.

[0027] In an embodiment of a thread former according to the present disclosure, when projected into a projection plane, the first partial surface has a first vertex angle formed between a first radius intersecting the tail end point of the first spine segment and a second radius intersecting the first midpoint on the first partial surface. The second partial surface has a second vertex angle formed between a third radius intersecting the front end point of the second spine segment and a fourth radius intersecting the second midpoint on the second partial surface. The first midpoint and the second midpoint are at an equal radial distance from the axis of rotation, which is equal to half of the sum of the maximum radial extension of the first spine segment and the radial distance of the lowest point from the axis of rotation. In this embodiment, the first vertex angle is greater than the second vertex angle. As a result, the stability of the caudal flank of the first spine segment is increased compared to the anterior flank of the second spine segment.

[0028] In an embodiment of a thread former according to the present disclosure, the first vertex angle is in the range of from 2.8° to 12.0°. In some embodiments, a smaller angle will not contribute enough to the strength of the spine segment. In some embodiments, a larger angle greater than 12° will not add more strength than the strength already achieved with an angle of 12°. For good enough strength, the preferred angle is in the range of 5° to 10°.

[0029] These characteristics of the caudal belly of the first spine segment and the anterior belly of the second spine segment can also be expressed by reference to the apical belly angle. Typically, increasing the first apical belly angle between the first partial surface of the one lubrication groove (which can also be expressed as the anterior belly of the one lubrication groove) increases the stability of the first spine segment. The first apical belly angle is formed between the periphery of the first spine segment and the anterior belly of the one lubrication groove. The second apical belly angle is formed between the periphery of the second spine segment and the second partial surface of the lubrication groove (which can also be expressed as the caudal belly of the one lubrication groove). In the sense of the present disclosure, the measurements provided by the first apical angle and the second apical angle can be similar to the measurements provided by the first apical belly angle and the second apical belly angle, so that both describe stable asymmetry according to the present disclosure. The first midpoint and the second midpoint are points defined on the first partial surface and the second partial surface so as to provide measurements for the first apical angle and the second apical angle, respectively.

[0030] In an embodiment of a thread forming machine according to the present disclosure, when projected into a projection plane, a first partial surface has a first base angle formed between a split radius intersecting the lowest point and a second radius intersecting a first midpoint on the first partial surface, and a second partial surface has a second base angle formed between a split radius intersecting the lowest point and a fourth radius intersecting a second midpoint on the second partial surface, wherein the first base angle is smaller than the second base angle.

[0031] Generally, increasing the first bottom angle increases the strength of the caudal belly of the first spine segment. In some embodiments, increasing the second bottom angle increases the cross-sectional area of ​​the lubrication groove, while ensuring the stability of the spine due to the smaller first bottom angle. Thus, the lubrication fluid can fully flow through the one lubrication groove.

[0032] The characteristics of the caudal flank of the first spine segment and the anterior flank of the second spine segment can also be expressed by reference to the bottom flank angle. This first bottom flank angle is formed between the first portion of the surface of the one lubrication groove and the line that intersects the segmentation radius perpendicularly at the lowest point. A second bottom flank angle is formed between the second portion of the surface of the one lubrication groove and the line that intersects the segmentation radius perpendicularly at the lowest point. According to this definition, reducing the bottom flank angle achieves increased strength and stability of the associated flank. According to some embodiments, a smaller second bottom flank angle can provide improved coolant flow.

[0033] In the sense of the present disclosure, the first base angle and the second base angle provide comparable measurements to the first base side belly angle and the second base side belly angle, and therefore both describe a stable asymmetry according to the present disclosure.

[0034] In an embodiment of a thread former according to the present disclosure, the first base angle is in the range from 3.8° to 53.0°. In some embodiments, smaller angles will not contribute enough to the stability of the spine segment. In some embodiments, larger angles greater than 53° will not add more stability than the stability already achieved by an angle of 53°. Preferred angles for sufficiently good stability are in the range of 5° to 40°.

[0035] In an embodiment of the thread former according to the present disclosure, when the trailing end point of the first spine segment, the leading end point of the second spine segment and the lowest point are projected into the projection plane, the trailing end point of the first spine segment, the leading end point of the second spine segment and the lowest point span an isosceles triangle. In this embodiment of the present disclosure, the equal length of the first waist and the second waist of the isosceles triangle are respectively arranged between the lowest point and the trailing end point and between the lowest point and the leading end point. This shape of the lubrication groove is and provides a trade-off between stability on the one hand and sufficient flow of the lubrication fluid on the other hand.

[0036] In an embodiment, the trailing end point of the first spine segment, the leading end point of the second spine segment, and the lowest point span an unequal-sided triangle. In this embodiment, the stability of one of the two spine segments is further enhanced. When compared to an isosceles triangle, the lowest point of the lubrication groove can be displaced in the direction of rotation to stabilize the leading end of the second spine segment, or displaced in the direction opposite to the direction of rotation to stabilize the trailing end of the first spine segment. BRIEF DESCRIPTION OF THE DRAWINGS

[0037] Further advantages, features and applications of the present disclosure will become apparent from the description of the following embodiments and the accompanying drawings. The foregoing introduction of the present disclosure and the following detailed description of the embodiments of the present disclosure will be better understood when read in conjunction with the accompanying drawings. It should be understood that the embodiments depicted are not limited to the precise arrangements and means shown. Unless otherwise indicated, similar reference numerals in different figures represent similar or corresponding parts.

[0038] Figure 1 is an isometric top view of a thread forming machine according to a first embodiment of the present disclosure.

[0039] Figure 2 yes Figure 1 Side view of a thread forming machine.

[0040] Figure 3 yes Figure 1 and Figure 2 Projection of the thread forming machine on a projection plane perpendicular to the axis of rotation.

[0041] Figure 4 yes Figure 3 An enlarged cross-sectional view of the projection.

[0042] Figure 5 is an isometric top view of a thread forming machine according to a second embodiment of the present disclosure.

[0043] Figure 6 yes Figure 5 Side view of a thread forming machine.

[0044] Figure 7 yes Figure 5 and Figure 6 Projection of the thread forming machine on a projection plane perpendicular to the axis of rotation.

[0045] Figure 8 yes Figure 7 An enlarged cross-sectional view of the projection. DETAILED DESCRIPTION

[0046] Figures 1 to 8The basic concept of a thread former 1 according to the present disclosure is visualized. The thread former 1 is designed for producing an internal thread in an existing hole in a metal workpiece without any chip cutting or chip removal operation. The thread is pressed into the material of the metal workpiece. The thread former 1 has a shaft 2, which has a first end 3 and a second end 4. A mounting segment 5 is connected to the first end 3 of the shaft 2 and a forming segment 6 is connected to the second end 4 of the shaft 2. During the forming operation, the mounting segment 5 is clamped in a spindle of a machine tool, wherein the machine tool provides for the rotation of the thread former 1 around a central rotation axis 7. The rotation axis 7 is a common central rotation axis of the shaft 2, the mounting segment 5 and the forming segment 6. The rotation axis 7 extends in the longitudinal direction of the thread former 1.

[0047] During operation of the thread forming machine 1, only the forming segment 6 engages with the workpiece. In order to reshape the cylindrical inner surface of the hole, the forming segment 6 comprises a plurality of ridge segments 9, which are located at the periphery of the forming segment 6. The ridge segments 9 are arranged on a helical path along the periphery of the forming segment 6 around the axis of rotation 7. The cross section of each of the ridge segments 9 thus corresponds substantially to the cross-sectional form of a groove in the internal thread to be produced.

[0048] The helix defined by the ridge segments 9 has the same hand as the internal thread to be formed in the workpiece. The thread former 1 thus has a natural direction of rotation 12 in which it can be screwed into a hole in the workpiece. Each element on the periphery of the forming segment 6 thus has a front portion or segment and a rear portion or segment.

[0049] The forming segment 6 has a plurality of axially spaced ridge segments 9 corresponding to the number of turns of the helix, when considered in an axial direction parallel to the axis of rotation 7. The maximum radial extension of the ridge segments 9 relative to the axis of rotation 7 increases in the axial direction from the front end 13 to the rear end 14 of the forming segment 6. Due to this increase, during the forming operation, the load on the thread forming machine 1 is distributed over a plurality of turns until the final depth of the internal thread is reached.

[0050] When using Figures 1 to 8 When the thread forming machine 1 of any of the figures manufactures internal threads, the thread forming machine 1, and in particular the forming section 6, is subjected to severe stress and high temperatures due to the interaction between the material of the forming section 6 and the metal workpiece. During the forming operation, the thread forming machine 1, and in particular the ridge section 9 in the forming section 6, is cooled and / or lubricated by a lubricating fluid. In order to effectively deliver the lubricating fluid to the hole and thereby to the location of the ridge section 9, a plurality of lubrication grooves 8 are provided. Figures 1 to 8 In the embodiment of the present invention, the thread forming machine 1 has five lubrication grooves 8 evenly distributed along the outer circumference of the forming section 6 .

[0051] Each of the five lubrication grooves 8 extends not only over the entire axial extension of the profile segment 6, but also into the shaft 2. Thus, lubrication fluid can be transferred from the shaft 2 into the lubrication groove 8 even if the profile segment 6 is screwed into the bore along its entire axial extension.

[0052] Now refer to Figure 3 and Figure 7 The design and function of each individual spine segment 9 is described. Figure 3 and Figure 7 Both show the projection of an arbitrary turn of the spiral formed by the ridge segment 9 in a projection plane perpendicular to the rotation axis 7. Each of the ridge segments 9 has a leading end point 13 and a trailing end point 14. The outer periphery of the ridge segment 9 has the shape of a symmetrical roof with an increasing side 15 and a decreasing side 16 and a point 17 of maximum radial extension from the rotation axis 7. The radial distance of the increasing side 15 of the ridge segment 9 increases from the leading end point 13 to the point 17 of maximum radial distance. The radial distance of the decreasing side 16 of the ridge segment 9 decreases from the point 17 of maximum radial extension to the trailing end point 14. The increasing side 15 and the decreasing side 16 of the ridge segment 9 have equal lengths and are arranged symmetrically about the point 17 of maximum radial extension.

[0053] Every two ridge segments of the plurality of ridge segments 9 are separated by one lubrication groove of the plurality of lubrication grooves 8. Thus, the trailing end point 14 of the first of the two ridge segments 9 forms the leading end point of the groove 8, and the leading end point 13 of the second of the two ridge segments 9 forms the trailing end point of the lubrication groove 8.

[0054] Some prior art thread formers with such symmetrical ridge segments tend to fail due to the tail of the ridge segment breaking. It has been found that this tendency to failure is due to the stresses generated during the forming operation, and the present disclosure addresses this tendency to failure by providing an asymmetrical shape of the lubrication groove 8 between every two ridge segments in the plurality of ridge segments 9.

[0055] On one hand, refer to Figures 1 to 4 And on the other hand refer to Figures 5 to 8 In both embodiments described, the asymmetry is configured such that the first partial surface 18 of the lubrication groove 8 provides more material to the trailing end of the first of the two ridge segments 9. Figures 1 to 4 In the first embodiment, due to the asymmetrical shape of the groove 8, the increase in material does not reduce the free cross-sectional area of ​​the lubricating groove 8. The shape of the second part surface 19 ensures that, despite the restricted cross-sectional area at the first part surface 18 of the lubricating groove 8, sufficient lubricating fluid can flow through the lubricating groove 8. The first part surface 18 can also be designated as the front belly of the lubricating groove 8. The second part surface 18 can also be designated as the caudal belly of the lubricating groove 8.

[0056] However, there may be other embodiments in which the design of the spine segments may differ from the reference Figures 1 to 8 The depicted design. In an embodiment, the second part surface 19 of the lubrication groove 8 can provide enhanced support for the front end of the second ridge segment 9 of the two ridge segments 9 by leaving more material at the front end of the second ridge segment 9. In other words, in such an embodiment with the same rotational direction 12, the shape of each of the lubrication grooves 8 will be reversed. This can be advantageous in designs where the point of maximum radial extension of the ridge segment is shifted towards the front end point 13.

[0057] Now refer to Figure 4 The enlarged, interrupted projection of FIG. 8 illustrates the exact shape and design of the lubrication groove 8 in more detail.

[0058] Figure 4 yes Figure 3 In the illustrated embodiment, the trailing end point 14 of the first ridge segment 9, the leading end point 13 of the second ridge segment 9 and the lowest point 20 on the surface of the lubrication groove 8 together span an isosceles triangle, the lowest point 20 having the smallest radial distance from the rotation axis 7.

[0059] The lubrication groove 8 is asymmetrical about the radius rd that intersects the surfaces 18, 19 of the lubrication groove 8 at the lowest point 20. However, at any point of the lubrication groove 8, the lubrication groove 8 is also asymmetrical about any other radius that intersects the surfaces 18, 19 of the lubrication groove 8. The radius rd is a dividing radius in the sense of the present disclosure and divides the lubrication groove 8 into two parts A and B. Figure 4 , the first portion A is to the left of the segmentation radius rd and includes a first partial surface 18 extending from the trailing end point 14 of the first ridge segment 9 to the lowest point 20. The second portion B is to the right of the segmentation radius rd and includes a second partial surface 19 extending from the lowest point 20 to the leading end point 13 of the second ridge segment 9.

[0060] exist Figures 1 to 4 In the embodiment of the invention, the second partial surface 19 is concavely curved along its entire extension from the lowest point 20 to the front end point 13. The first partial surface 18 is shorter than the second partial surface 19. Expressed differently, when Figure 4 When viewed in the projection view of FIG. 1 , the length of the first partial surface 18 is shorter than the length of the partial surface 19. Therefore, more material is left at the trailing end of the first ridge segment 9 than at the leading end of the second ridge segment 9. In some prior art forming machines, both surfaces of the lubrication groove have a concave shape. In contrast, the first partial surface 18 is approximately a straight line along most of the portion.

[0061] exist Figures 1 to 8In both embodiments shown in the drawings, an upper ventral angle γ1 is formed between the first partial surface 18 and the tail side 15 of the spine segment 9, and a second upper ventral angle γ1 is formed between the second partial surface 19 and the front side 16 of the second spine segment 9. In order to strengthen the tail end of the first spine segment 9, the first upper ventral angle γ1 is greater than the second ventral angle γ2.

[0062] The asymmetric lubrication groove 8 can be expressed in different terms: the first part surface 18 includes a first vertex angle α1. The first vertex angle α1 is formed between a first radius r1 intersecting the trailing end point 14 of the first ridge segment 9 and a second radius r2 intersecting the first midpoint 23 on the first part surface 18. The second part surface 19 has a second vertex angle α2. The second vertex angle α2 is formed between a third radius r3 intersecting the leading end point 13 of the second ridge segment 9 and a fourth radius r4 intersecting the second midpoint 24 on the second part surface 19. The first midpoint 23 and the second midpoint 24 are at an equal radial distance from the rotation axis 7, which is equal to half the sum of the maximum radial extension of the first ridge segment (i.e., the radial distance of the point 17 from the rotation axis 7) and the radial distance of the lowest point 20 from the rotation axis 7. Since the first apical side belly angle γ1 is greater than the second apical side belly angle γ2, the first vertex angle α1 is also greater than the second vertex angle α2.

[0063] In addition to reinforcing the radially outer portion of the trailing end of the first spine segment 9, a reinforcing effect is also provided at the radially inner portion of the trailing end of the first spine segment 9. Figures 1 to 8 In the embodiment of FIG. 1 , this additional reinforcement is provided by a smaller first bottom side belly angle δ1 formed between a straight line 21 perpendicular to the segmentation radius rd and intersecting the lowest point 20 and the first part surface 18 .

[0064] The second bottom flank angle δ2 is formed between a straight line 21 perpendicular to the segmentation radius rd and intersecting the lowest point 20 and the second part surface 19. Generally, also reducing the bottom flank angle δ2 achieves an increase in the strength and stability of the associated flank. In the first embodiment, the smaller second bottom flank angle δ2 increases the cross-sectional area of ​​the lubrication groove, which improves the coolant flow.

[0065] Alternatively, the relationship between the first partial surface 18 and the second partial surface 19 can be described in terms of a first base angle β1 and a second base angle β2. The first base angle β1 is formed between a splitting radius rd intersecting the lowest point 20 and a second radius r2 intersecting the first midpoint 23 on the first partial surface 18. The second base angle β2 is formed between the splitting radius rd and a third radius r3 intersecting the second midpoint 24 on the first partial surface 19. The first base angle β1 is smaller than the second base angle β2. According to this definition, increasing the first base angle β1 increases the strength of the caudal belly of the first spine segment. In accordance with Figure 4In the first embodiment, the increase in the second bottom angle β2 increases the cross-sectional area of ​​the lubrication groove, while the stability of the ridge is ensured due to the smaller first bottom angle β1. Thus, the lubrication fluid can fully flow through the one lubrication groove.

[0066] Each of the lubrication grooves 8 of the thread forming machine 1 has a similar shape to the reference shape when projected into the projection plane. Figure 4 Same shape as discussed.

[0067] Now refer to Figure 8 The enlarged cross-sectional view shown is discussed according to Figures 5 to 8 The lubrication groove 8 of the second embodiment is designed.

[0068] When with Figures 1 to 4 When compared with the embodiment of Figures 5 to 8 The embodiment of the embodiment does not include a lubrication groove 8 comprising an isosceles triangle. The triangle spanned by the tail end point 14 of the first spine segment 9, the front end point 13 of the second spine segment 9 and the lowest point 20 is a scalene triangle. Compared to the first embodiment, the lowest point 20 has been shifted in the direction opposite to the rotation direction 12, i.e. towards the tail side of the lubrication groove 8. As a result, the tail of the first spine segment 9 is even more reinforced.

[0069] Again, the first top side abdominal angle γ1 is greater than the second top side abdominal angle γ2. Therefore, the relationship between the first top angle α1 and the second top angle α2 is also the same as the reference Figures 1 to 4 Therefore, the first vertex angle α1 is greater than the second vertex angle α2. Figures 5 to 8 In the embodiment, the first partial surface 18 and the second partial surface 19 have a cross section that can be approximately a straight line.

[0070] It should be noted that, as can be easily understood by those skilled in the art, features described in conjunction with one embodiment may also be used in other embodiments.

[0071] Although the present disclosure has been described in detail with reference to the accompanying drawings, this description is only an example and is not to be considered as limiting the scope of protection defined by the claims.

[0072] In the claims, the word "comprising" does not exclude other elements or steps, and the indefinite article "a" or "an" does not exclude a plurality. The mere fact that certain features are claimed in different claims does not exclude their combination. Reference signs in the claims shall not be regarded as limiting the scope of protection.

[0073] Reference numerals list

[0074] 1 Thread forming machine

[0075] 2 Axis

[0076] 3 First End

[0077] 4 Second End

[0078] 5 Installation section

[0079] 6 Forming section

[0080] 7 Axis of rotation

[0081] 8 Lubrication grooves

[0082] 9 Segment

[0083] 10 Front end of the forming section

[0084] 11 The rear end of the forming section

[0085] 12 Direction of rotation

[0086] 13 Front end point

[0087] 14 End point

[0088] 15 Enlargement side

[0089] 16 Reduce side

[0090] 17 Point of maximum radial extension

[0091] 18 First part surface

[0092] 19. Part II Surface

[0093] 20 Lowest point

[0094] 21 A straight line perpendicular to the lowest point 20

[0095] 22 A straight line connecting the end point and the front point

[0096] 23 First midpoint

[0097] 24 Second midpoint

[0098] A The first part of the lubrication groove 8

[0099] B Second part of lubrication groove 8

[0100] rd segmentation radius

[0101] r1 first radius

[0102] r2 Second radius

[0103] r3 The third radius

[0104] r4 fourth radius

Claims

1. A thread forming machine (1) for producing an internal thread in a metal workpiece, the thread forming machine (1) comprising: - a shaft (2) having a first end (3) and a second end (4), a mounting section (5) connected to the first end (3) of the shaft (2) for mounting the thread former (1) to a spindle of a machine tool, and - a shaped section (6) connected to said second end (4) of said shaft (2), wherein the shaft (2), the mounting section (5) and the forming section (6) have a common central rotation axis (7), the rotation axis (7) extending in a longitudinal direction, wherein the forming section (6) comprises a plurality of lubrication grooves (8) extending parallel to the rotation axis (7), The forming section (6) comprises a plurality of ridge sections (9) extending around the forming section (6), wherein the ridge sections extend along a spiral. - wherein the plurality of ridge segments (9) are arranged for forming the internal thread in the metal workpiece, and - wherein, in the circumferential direction, every two ridge segments of the plurality of ridge segments (9) are separated by one lubrication groove of the plurality of lubrication grooves (8), At least one of the lubrication grooves (8) is asymmetric about any radius intersecting a surface (18, 19) of the one lubrication groove (8) when projected into a projection plane perpendicular to the rotation axis (7), It is characterized in that When each of the plurality of ridge segments (9) is projected into the projection plane, each of the plurality of ridge segments (9) has a leading end point (13) at the periphery of the forming segment (6) and a trailing end point (14) at the periphery of the forming segment (6), The surface of the one lubricating groove (8) extends from the trailing end point (14) of the first of the two ridge segments (9) to the leading end point (13) of the second of the two ridge segments (9), The surface of the one lubrication groove (8) has a lowest point (20), and the radial distance of the lowest point (20) from the rotation axis (7) is the smallest, The lubrication groove (8) comprises two partial surfaces, A first partial surface (18) extends from the trailing end point (14) of the first spine segment to the lowest point (20), A second partial surface (19) extends from said lowest point (20) to said front end point (13) of said second ridge segment, The first partial surface (18) has a first vertex angle (α1) formed between a first radius (r1) intersecting the trailing end point (14) of the first ridge segment and a second radius (r2) intersecting a first midpoint (23) on the first partial surface (18), The second partial surface (19) has a second vertex angle (α2), the second vertex angle (α2) being formed between a third radius (r3) intersecting the front end point (13) of the second ridge segment and a fourth radius (r4) intersecting the second midpoint (24) on the second partial surface (19), The radial distance between the first midpoint (23) and the second midpoint (24) from the rotation axis (7) is equal to half the sum of the maximum radial extension of the first spine segment and the radial distance between the lowest point (20) and the rotation axis (7), and wherein The first vertex angle (α1) is greater than the second vertex angle (α2).

2. The thread forming machine (1) according to claim 1, wherein: Any radius is a dividing radius (rd), which divides the one lubrication groove (8) into a first part (A) and a second part (B), wherein the dividing radius (rd) intersects the surface of the one lubrication groove (8) at the lowest point (20) having the smallest radial distance from the rotation axis (7).

3. The thread forming machine (1) according to any one of claims 1 to 2, wherein: At least the one lubrication groove (8) is asymmetrical along the entire axial extension of the one lubrication groove (8) in the profiled section (6) with respect to any radius intersecting the surface of the one lubrication groove (8).

4. The thread forming machine (1) according to claim 2, wherein: When the first portion (A) and the second portion (B) of the one lubrication groove (8) are projected into the projection plane, the first portion (A) of the one lubrication groove (8) is limited by the first portion surface (18), and the second portion (B) of the one lubrication groove (8) is limited by the second portion surface (19), wherein a cross-sectional area of ​​the first portion (A) is smaller than a cross-sectional area of ​​the second portion (B).

5. The thread forming machine (1) according to any one of claims 1 to 2, wherein: When the second partial surface (19) and the first partial surface (18) are projected into the projection plane, the second partial surface (19) has a concave curvature along its entire extension from the lowest point (20) to the front end point (13) of the second ridge segment, and the first partial surface (18) is shorter than the second partial surface (19).

6. The thread forming machine (1) according to any one of claims 1 to 2, wherein: When the first partial surface (18) is projected into the projection plane, at least a portion of the first partial surface (18) is straight.

7. The thread forming machine (1) according to any one of claims 1 to 2, wherein: The first vertex angle (α1) is in the range from 2.8 degrees to 12.0 degrees.

8. The thread forming machine (1) according to claim 2, wherein: When the first partial surface (18) is projected into the projection plane, The first partial surface (18) has a first base angle (β1), the first base angle (β1) being formed between the dividing radius (rd) intersecting the lowest point (20) and the second radius (r2) intersecting the first midpoint (23) on the first partial surface (18), The second partial surface (19) has a second base angle (β2), which is formed between the dividing radius (rd) intersecting the lowest point (20) and the fourth radius (r4) intersecting the second midpoint (24) on the second partial surface (19), The radial distance between the first midpoint (23) and the second midpoint (24) and the rotation axis (7) is equal to half the sum of the maximum radial extension of the first ridge segment and the radial distance between the lowest point (20) and the rotation axis (7), and The first base angle (β1) is smaller than the second base angle (β2).

9. The thread forming machine (1) according to claim 8, wherein: The first base angle (β1) is in the range from 3.8 degrees to 53.0 degrees.

10. The thread forming machine (1) according to any one of claims 1 to 2, wherein: When the tail end point (14) of the first ridge segment, the front end point (13) of the second ridge segment and the lowest point (20) are projected into the projection plane, the tail end point (14) of the first ridge segment, the front end point (13) of the second ridge segment and the lowest point (20) span an isosceles triangle.

11. The thread forming machine (1) according to any one of claims 1 to 2, wherein: When the tail end point (14) of the first ridge segment, the front end point (13) of the second ridge segment and the lowest point (20) are projected into the projection plane, the tail end point (14) of the first ridge segment, the front end point (13) of the second ridge segment and the lowest point (20) span an unequal-sided triangle.

12. The thread forming machine (1) according to any one of claims 1 to 2, wherein: At least one of the lubrication grooves (8) extends in the profiled section (6) and the shaft (2).

13. The thread forming machine (1) according to any one of claims 1 to 2, wherein: When all of the plurality of lubrication grooves (8) are projected onto the projection plane, all of the plurality of lubrication grooves (8) have the same shape.

Images